Amazon offers the AmazonBasics 1.0mm Ballpoint Pen 100-Pack in Black/Blue for $3.61 with free shipping when you check out via Subscribe & Save. That's $3 off list and the lowest price we could find. (For further comparison, Staples sells a 60-pack of similar pens for $5.99.) It includes 50 black pens and 50 blue pens.

Be sure to cancel your subscription once your order ships to avoid being billed for further shipments.